Semiconductor device and method of manufacturing a semiconductor device

ABSTRACT

A semiconductor device includes a memory region, a plurality of bit lines in the memory region, a first low-k dielectric layer on each sidewall of each bit line, a plurality of storage node regions between the bit lines, and a second low-k dielectric layer surrounding each storage node region.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application and claims the benefit ofU.S. non-provisional application Ser. No. 15/854,827, which was filed onDec. 27, 2017 and is incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates generally to a semiconductor device, morespecifically, to a semiconductor device with low-K materials to reduceparasitic capacitance.

2. Description of the Prior Art

Semiconductor devices are widely used in an electronic industry becauseof their small size, multi-function and/or low manufacture costs.Semiconductor devices are categorized as semiconductor devices storinglogic data, semiconductor logic devices processing operations of logicaldata, hybrid semiconductor devices having both the function ofsemiconductor memory devices and the function of semiconductor logicdevices and/or other semiconductor devices.

Semiconductor devices may generally include vertically stacked patternsand contact plugs electrically connecting the stacked patterns to eachother. As semiconductor devices have been highly integrated, a spacebetween the patterns and/or a space between the pattern and the contactplug have been reduced. Thus, a parasitic capacitance between thepatterns and/or between the pattern and the contact plug may beincreased. The parasitic capacitance may cause performance deterioration(e.g., reduction of an operating speed) of semiconductor devices. Forthis reason, how to reduce parasitic capacitance in semiconductordevices is an urgent task to research and develop in the semiconductorindustry.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method ofmanufacturing a semiconductor device. The method features the low-Kdielectric layer disposed along two sides of bit lines and surroundingstorage nodes to effectively reduce the parasite capacitance in devices,and the process steps of the present invention may be integrated withthe process steps of logic devices in peripheral regions withoutadditional process cost or time.

To achieve the above-mentioned purpose, a semiconductor device isprovided in one embodiment of the present invention. The semiconductordevice includes a memory region, a plurality of bit lines in the memoryregion, a first low-k dielectric layer on each sidewall of each bitline, a plurality of storage node regions between the bit lines, and asecond low-k dielectric layer surrounding each storage node region.

To achieve the above-mentioned purpose, a method of manufacturing asemiconductor device is provided in one embodiment of the presentinvention. The steps of the method include providing a substrate with amemory region and a logic region thereon, forming bit lines and logicgates respectively in the memory region and the logic region, whereinstorage node regions are defined between bit lines, forming a firstlow-K dielectric layer on sidewalls of bit lines, forming doped-siliconlayer in each storage node region between bit lines, wherein the topsurface of doped-silicon layer is lower than the top surface of bitlines, forming a second low-K dielectric layer on sidewalls of thestorage node regions, and filling up the storage node regions in thememory region with metal plugs.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the embodiments, and are incorporated in and constituteapart of this specification. The drawings illustrate some of theembodiments and, together with the description, serve to explain theirprinciples. In the drawings:

FIGS. 1-11 are cross-sectional views schematically showing the processflow of manufacturing a semiconductor device in accordance with oneembodiment of the present invention; and

FIG. 12 is a top view of a semiconductor device in accordance with oneembodiment of the present invention.

It should be noted that all the figures are diagrammatic. Relativedimensions and proportions of parts of the drawings have been shownexaggerated or reduced in size, for the sake of clarity and conveniencein the drawings. The same reference signs are generally used to refer tocorresponding or similar features in modified and different embodiments.

DETAILED DESCRIPTION

In the following detailed description of the present invention,reference is made to the accompanying drawings which form a part hereofand is shown by way of illustration and specific embodiments in whichthe invention may be practiced. These embodiments are described insufficient details to enable those skilled in the art to practice theinvention. Other embodiments may be utilized and structural, logical,and electrical changes may be made without departing from the scope ofthe present invention. The following detailed description, therefore, isnot to be taken in a limiting sense, and the scope of the presentinvention is defined by the appended claims.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element, component, region, layer and/or section fromanother. Thus, a first element, component, region, layer or sectiondiscussed below could be termed a second element, component, region,layer or section without departing from the teachings of the disclosure.

The terminology used herein to describe embodiments of the inventiveconcepts is not intended to limit the scope of the inventive concepts.The use of the singular form in the present document should not precludethe presence of more than one referent. In other words, elements of theinventive concepts referred to in the singular may number one or more,unless the context clearly indicates otherwise. It will be furtherunderstood that the terms “comprises,” “comprising,” “includes,” and/or“including,” when used herein, specify the presence of stated features,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof.

The process flow of manufacturing a semiconductor device of the presentinvention will be described hereinafter with reference to FIG. 1 to FIG.11 in sequence. Please refer to FIG. 1. According the method ofmanufacturing a semiconductor device in the present invention, asemiconductor substrate 100 is first prepared to serve as the base forcomponents to be disposed thereon. The semiconductor substrate mayinclude silicon substrate, silicon-germanium (SiGe) substrate, orsilicon-on-insulator (SOI) substrate, etc, wherein a memory region 10 isdefined thereon for disposing memory arrays consisting of multiplememory cells, and a logic region 20 is defined thereon surrounding thememory region 10 for disposing other logic or functional circuits, suchas sense amplifier, address buffer, and address decoder, etc. Someprocess steps described in following embodiments are only performed inone of the memory region 10 and the logic region 20, while others may beperformed in both regions.

The semiconductor substrate 100 includes active regions 102 and fieldoxide regions 104 (or shallow trench isolations, STI). Field oxideregion 104 may be formed by filling up the preformed field oxidetrenches with field insulating material, such as silicon oxide. Theactive regions 102 are defined by the surrounding field oxide region104. The memory region 10 and logic region 20 of the semiconductorsubstrate 100 are pre-formed respectively with bit lines 110 and logicgates 210 thereon, wherein the bit line 110 may include from bottom totop a bit line contact plug 112 (ex. a doped poly-silicon layer or anamorphous silicon layer extending into the semiconductor substrate 100and connecting the active region thereunder), a bit line electrode 114(ex. Ti/TiN/W multilayer metal structure), and a hard mask 116 (ex. asilicon nitride layer). A metal silicide layer 118 may be further formedbetween bit line contact plug 112 and bit line electrode 114, forexample, by the reaction of lowest portions of bit line electrode withthe silicon surface, to connecting the bit line electrode 114 and thebit line contact plug 112. In the manufacturing process, trenches 106may be formed between two sides of bit line gate 110 and substrate sincethe width of opening of bit line contact formed in previous etch processis larger than the width of bit line 110 itself.

Refer again to FIG. 1. The logic gate 210 on the logic region 20 ofsemiconductor substrate 100 may include agate dielectric layer 212 (ex.a silicon oxide layer), a gate electrode layer 214 (ex. a poly-siliconlayer), and a capping layer 216 (ex. a silicon nitride layer). In theembodiment of present invention, the logic gate 210 on the logic region20 and the bit line gate 110 on the memory region 10 are formed indifferent processes. However, in other embodiment, the logic gate 210 onthe logic region 20 and the bit line gate 110 on the memory region 10may be formed in the same process.

Please refer to FIG. 2. After bit lines 110 and logic gates 210 areformed, a first spacer layer 120 and a second spacer layer 122 areconformally formed on the memory region 10 and logic region 20 andcompletely cover thereon, wherein the first spacer layer 120 may be asilicon nitride layer or a silicon carbon nitride layer plus an oxidelayer to function as a barrier layer for bit lines. The second spacerlayer 120 may be another silicon nitride layer with distinctive etchselectivity compared to the oxide layer of first spacer layer 120. Thefirst spacer layer 120 and the second spacer layer 122 would fill up thetrenches 106 at both sides of the bit line 110. Alternatively, in someembodiment, the trench 106 is not filled up on purpose to form gapinside.

Please refer to FIG. 3. After the first spacer layer 120 and secondspacer layer 122 are formed, a third spacer material are formed in thelogic region 20 and then are performed with an anisotropic etch processto form spacers 218 at both sides of the logic gates 210, wherein thespacer 218 is made up of the first spacer layer 120, the second spacerlayer 122 and the third spacer layer 124. Please note that there is nothird spacer layer 124 remaining in the memory region 10 in this stage.The third spacer layer 124 may be selectively removed from memory region10 by using photoresist and buffered oxide etch (BOX) process.Furthermore, the portion of second spacer layer 122 not covered by thethird spacer layer 124 on the memory region 10 is then removed by usingother etchants with appropriate etch selectivity. Thus, only the portionof second spacer layer 122 inside the trenches may remain and the firstspacer layer 120 is exposed.

Please refer to FIG. 4. After the second spacer 122 is removed, a firstlow-K dielectric layer 126 is formed conformally on the memory region 10and completely covers the bit lines 110. The example of low-K materialmay include, but not limited to, hydrogen silsesquioxane (HSQ),methyl-silsesquioxane (MSQ), polyphenylene oligomer, methyl dopedsilica, organo-silicate glass, or porous silicide, etc. Please note thatthe first low-K dielectric layer 126 is not formed on the logic region20 in this embodiment. On the other hand, an ion implantation process isperformed on the logic region 20 to form source/drain 220 between thespacers 218 and outer field oxide region 104 formed in previousprocesses.

Please refer to FIG. 5. After the first low-K dielectric layer 126 isformed, an anisotropic etch process is performed to remove the firstlow-K dielectric layer 126 and the first spacer layer 120 on the surfaceof memory region 10, so that only the first low-K dielectric layer 126on sidewalls of the bit lines 110 remains and the active regions 102 ofmemory region 10 are exposed. In this embodiment, storage node regions127 are defined between bit lines 110 to be preserved for disposing thestorage node structures of the memory cells. In the embodiment of thepresent invention, The approach of forming the first low-K dielectriclayer 126 a on sidewalls of the bit lines may help to reduce theparasite capacitance induced by close spacing between bit lines andstorage node therearound, thereby improving the device's performance.

Please refer to FIG. 6. A contact etch stop layer (CESL) 128, such as asilicon nitride layer, is then formed conformally on the memory region10 and logic region 20. The material of contact etch stop layer 128 hasgood etch selectivity compared to the material of interlayer dielectric(ILD) to be formed in later process.

Please refer to FIG. 7. After the contact etch stop layer 128 is formed,an interlayer dielectric 130 is blanket-deposited on the memory region10 and the logic region 20, and a chemical mechanical polishing (CMP)process is performed to the process surface until the top surfaces ofbit lines 110 and logic gates 210 are flush. The interlayer dielectric130 would fill up the storage node regions 127 between bit line gates110.

Please refer to FIG. 8. After the interlayer dielectric 130 is formed,the interlayer dielectric 130 in the memory region 10 is removed byusing the etchants dedicated for silicon oxide material. An anisotropicetch process is further performed to remove the contact etch stop layer128 on the surface of memory region 10, so that only the contact etchstop layer 128 a on sidewalls of bit lines 110 remains and the activeregions 102 in the memory region 10 are exposed. In this way, thestorage node regions 127 would be preserved again for the components ofstorage nodes.

Please refer to FIG. 9. The doped silicon layer 132, such as aphosphorus-doped silicon layer, is then formed in the storage noderegions 127 between bit lines 110 in the memory region 10, to functionas a lower storage node structure. The top surface of the doped siliconlayer 132 would be lower than the top surface of surrounding bit linegates 110, so that the storage node region 127 is not filled up by thedoped silicon layer 132. The doped silicon layer 132 may be formed byfollowing processes: first, covering a doped silicon material on thememory region 10. The doped silicon material would fill up the storagenode regions 127 between bit lines 110. An etch back process is thenperformed to remove the doped silicon material outside the storage noderegions 127 until the top surface of doped silicon material reaches apredetermined level lower than the top surface of surrounding bit lines110. The lower storage node structure is therefore completed. Theremaining space on the storage node regions 127 may be preserved for theformation of upper storage node structure. Please note that in thisembodiment, there is no doped silicon layer formed in the logic region20.

Please refer to FIG. 10. After the doped silicon layer 132 is formed inthe storage node regions 127, a second low-K dielectric layer 134 isthen conformally formed on the memory region 10. The second low-Kdielectric layer 134 covers the surface of bit line gates 110 andremaining storage node regions 127. The material of second low-Kdielectric layer 134 may be the same as the one of first low-Kdielectric layer 126, which may include, but not limited to, hydrogensilsesquioxane (HSQ), methyl-silsesquioxane (MSQ), polyphenyleneoligomer, methyl doped silica, organo-silicate glass, or poroussilicide, etc. Please note that in this embodiment, no second low-Kdielectric layer 134 is formed on the logic region 20.

Please refer to FIG. 11. After the second low-K dielectric layer 134 isformed, an etch back process is then performed to remove the secondlow-K dielectric layer 134 on the top surface of bit lines 110 and onthe bottom surface of storage node region 127. Only the portion ofsecond low-K dielectric layer 134 a on sidewalls between bit linesremains in the region, so that the doped silicon layers 132 in thestorage node regions 127 are exposed. In addition, a photolithographicprocess and an etch process are further performed on the logic region 20to form contact holes 222 extending downward to the source/drain 220below in the interlayer dielectric 130.

Refer again to FIG. 11. The remaining storage node regions 127 in thememory region 20 and the contact holes 222 in the logic region 10 arefilled up with metal to form contact plugs 136 and 224 respectively. Thecontact plugs 136 and 224 may include multilayer structure such asTi/TiN/W and connect electrically and respectively with the dopedsilicon layer 132 and the source/drain 220 thereunder. The contact plug136 on the memory region 20 is connected with the doped silicon layer132 to function as an upper storage node structure. In addition, a metalsilicide process may be performed before the filling process of contactplugs, to form metal silicide layers on exposed surfaces of the dopedsilicon layer 132 and source/drain 220 and thereby establishing goodelectrical connection with the contact plugs to be filled in laterprocess.

Please refer to FIG. 12, which is a schematic top view of asemiconductor device in accordance with one embodiment of the presentinvention. In the embodiment of the present invention, the first low-Kdielectric layer 126 a formed along the sidewalls of bit lines 110 inearly step of the process flow may effectively reduce the parasitecapacitance induced by close spacing between bit lines and surroundingstorage nodes. Furthermore, since the second low-K dielectric layer 134a is formed and disposed on the sidewalls surrounding the storage noderegions 127 defined by bit lines 110 (horizontal direction) and the wordlines 310 (vertical direction) in late step of the process flow, theentire storage node region may be enclosed by the second low-Kdielectric layer 134 a, so that the issue of parasite capacitance may befurther improved.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A semiconductor device, comprising: a memoryregion; a plurality of bit lines in said memory region; trenches at twosides of each said bit line; a first low-k dielectric layer on eachsidewall of each said bit line; a plurality of storage node regionsbetween said bit lines; a second low-k dielectric layer surrounding eachsaid storage node region; and a first spacer layer conformally on saidtrench and said bit line and a second spacer layer filling up saidtrench on said first spacer layer, wherein said first low-k dielectriclayer is on said first spacer layer on said sidewall of said bit line.2. The semiconductor device of claim 1, wherein said storage noderegions are demarcated by said bit lines and a plurality of word lines,and said bit lines are perpendicular to said word lines.
 3. Thesemiconductor device of claim 1, further comprising a contact etch stoplayer between said first low-k dielectric layer and said second low-kdielectric layer.
 4. The semiconductor device of claim 1, wherein saidbit line comprises: a bit line contact plug; a bit line electrode onsaid bit line contact plug; and a hard mask on said bit line electrode.5. The semiconductor device of claim 4, wherein said bit line contactplug is a doped poly-silicon layer or an amorphous silicon layer.
 6. Thesemiconductor device of claim 4, wherein said bit line electrodecomprises Ti/TiN/W multilayer metal structure.
 7. The semiconductordevice of claim 4, further comprising a metal silicide layer betweensaid bit line contact plug and said bit line electrode.
 8. Thesemiconductor device of claim 1, further comprising a doped siliconlayer on each said storage node region and a contact plug on each saiddoped silicon layer, and said second low-k dielectric layer surroundsonly said contact plug on said doped silicon layer.
 9. The semiconductordevice of claim 1, wherein a material of said first low-k dielectriclayer or said second low-k dielectric layer comprises hydrogensilsesquioxane (HSQ), methyl-silsesquioxane (MSQ), polyphenyleneoligomer, methyl doped silica, organo-silicate glass or porous silicide.